public class Tractor {
    //载重、体积
    String load,volume;

    public Tractor(String load, String volume) {
        this.load = load;
        this.volume = volume;
    }

    //启动、加速
    public void start() {
        System.out.println("启动");
    }

    public void hasten() {
        System.out.println("加速");
    }
}